The most common abnormal heart rhythm, atrial fibrillation, occurs when the upper heart chambers quiver instead of contracting regularly, allowing blood to pool inside the heart. In a healthy person who had a few too many drinks, the fibrillation is usually fleeting. But if it persists, it can lead to congestive heart failure or stroke.

"If that blood is allowed to sit still for long enough it clots," said Gillinov. "If the heart squeezes out a clot, it can lodge in the small arteries of the brain and cause a stroke."

The phrase "holiday heart syndrome" was coined in 1978 when researchers detected heart rhythm abnormalities in 24 study participants, none of whom had a history of heart disease. What they did have was too many drinks.

Since then, several studies have confirmed alcohol's heart rhythm-disturbing effects.

"Heavy alcohol use can lead to dehydration," said Dr. Malissa Wood, co-director of the Corrigan Women's Heart Health Program at the Massachusetts General Hospital Heart Center. "It can also deplete electrolytes like potassium and magnesium. And it may also affect the way the heart responds to adrenaline in your own body."

Although the holidays pose special challenges to heart health, they also offer unique opportunities to boost it.

"The holidays are a great opportunity to give your family the gift of better health through information," said Wood. "Heart disease is the number one killer in women and men. And we can prevent it by maintaining a healthy weight, exercising, watching salt and fat intake, not smoking and controlling blood pressure."